(a) Field of the Invention
The present invention relates to a charging device with a multiple stage or xe2x80x9cmulti-stepxe2x80x9d voltage charging source, and more particularly to one that has a (dis)chargeable storage device on a load side that is charged by the multi-step charging source up to a preset voltage, after which the charging status is maintained by means of a smaller charging current supplied by a stage of the charging source with higher voltage, or the charging current is cut off by (i) operating a primary control switch connected in series with the charging circuit, or (ii) turning the primary switch connected in series with a charging circuit to an open circuit condition to thereby cut off charging of the (dis)chargeable storage device.
(b) Description of the Prior Art
A conventional single step voltage charging source usually requires an analog resistance device known to have high thermal loss for regulating and controlling output voltage and current, or a pulse-width-modulation (PWM) device known to generate higher electromagnetic interference (EMI) noise to regulate and control the output voltage and current. The charging device of the multi-step voltage charging source of the present invention, on the other hand, simultaneously reduces thermal loss and EMI noise level.
The primary purpose of the present invention is to provide a charging device with a multi-step voltage charging source that has a (dis)chargeable storage device on a load side to be charged by the multi-step charging source up to preset voltage, after which the charging status is maintained by a smaller charging current supplied by a stage of the charging source with higher voltage, or the charging current is cut off by operating a primary control switch connected in series with a charging circuit, or by turning the primary switch connected in series with a charging circuit to open circuit, thus cutting off charging of the (dis)chargeable storage device.